From the op: "However, the thing is I think some people address topics like these in poor taste, as their main goal isn't to criticize sex offenders, murder, etc. but rather the comedy itself is the main goal."
How is it bad taste to have comedy as a main goal for a joke?
I think that there should be no limit. However many use this as an excuse to make hateful jokes to deliberately insult someone.So I think that the motive for the joke is the most important thing in determining whether it should be accepted or not.
For example if a child tells a funny joke about dead babies for a mother, that just lost her baby. If the child did it thinking that it would be funny and did´t mean to hurt anyone, then it should be fine. But of course the child might feel guilty and bad, if the mother for example started to cry, because of that joke.
So my point is that everything should be allowed if the intent is good for example to make others laugh and not to hurt anyone. And it is important to learn to know when and what jokes to tell to others, be sensitive and understand that people are different.
:D to the abortion joke!